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Transmission risk


We are expecting a boy.
As part of prenatal diagnosis, the father and I made blood screening for cystic fibrosis.
Initially, the results came back negative (with the set of the thirty most common mutations).
However, this Friday we learned I was carrying an unknown mutation of the gene cftr (not referenced and which we do not know if pathogenic).
On the side of dad, pushed test was also made clear and negative.
The lab concluded that a risk of 1/200 for the baby.
This result seems very high to the extent that the father is healthy and I confess that 37sa this type of result is very worrying.
Thank you in advance for lighting you can give us

CFTR gene mutation detection rate by a commercial kit detects the 30 most common mutations in France say about 85%. The CFTR mutation carrier rate in the general population is 1/34 considering the incidence of CF in France (1 in 4700 births).
Despite the negative outcome of your spouse test, it persists a risk to you as a couple, in each pregnancy, to have a child with the disease = 1/34 * 1/2 * 15/100 * 1/2 = 1/906 (on condition that the unknown "mutation" you are carrying is deleterious is to say cause of CF symptoms).

This risk about 1/1000 is 4 times higher than the general population. In this situation, some genetic laboratories use high-throughput sequencing techniques that can detect to date 98% of the CFTR mutations. The negative results of such research for your spouse will give a risk for you couple to give birth to a sick child = 1/34 * 1/2 * 2/100 * 1/2 = 1/6800 say less than for the general population (still on condition that the unknown "mutation" you are carrying is deleterious).
If you wish you can to contact the CF Center closest to your home that will direct you to a genetics laboratory with these techniques. Access to the map of the CFCs by clicking on the following link:

Hope this answer can help.
Best wishes
Gilles RAULT, MD, Roscoff CF Center